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  1. #1
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    half controlled rectifier using scr

    I want to design a half controlled SCR rectifier with PIC16f877 for driving a 15kW DC motor. is it possible? what do you suggest me to do? I have problems about firing thyristor and turning them off. they are not GTOs. I found TCA785 IC for single phase half controlled rectifier control. is it a good choice? what is the other possibilities? Should I use pulse transformer or MOC3021/51? Is there a sample circuit? for 15kW dc motor,at the end of the positive cycle, does thyritor turn off by self commutation or should I use forced commutation?

    thanks...

    •   Alt13th October 2006, 23:27

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    motor control rectifier scr pulse transformer

    Use step down transformer to covert 230v AC to 5V & give it to Zero crossing detector OPAMP i.t TL082P .ZCD convert AC to Square wave. Give sq. wave output of ZCD to intergrator. Compare out put of integrator with ref. volt which give the pulse. And the pulse with the timer out put & give it to opto isolator & give out put of opto isolator to Gate Cathode of thyristor.

    Added after 3 minutes:

    also fo 15kw dc motor select the hald controlled rectifier having current capacity more than 80A.

    semikton , thosiba are the supplier of the such power thyristor & IGBT



    •   Alt16th May 2008, 09:15

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  3. #3
    FvM
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    4251 rectifier

    Usual opto-tricas (e. g. MOC302x) are more sensitive to voltage transients than thyristors, so it would considerably degrade the circuit performance. Pulse transformers are the traditional solution.

    Depending on the motor type a series inductance may be required to limit the rate of current increase to a bearable value, e. g. to meet the thyristor specification.



    •   Alt16th May 2008, 09:37

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    control scr rectifier circuit

    we have used IL4218 for the thyristor firing .find the attached datasheet.



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    half controlled scr

    we have used IL4218 for the thyristor firing .find the attached datasheet.


    pulse out - IL4218 led - isolated DIAC - output Gate-kathode thyristor 1 (positive cycle

    pulse out - IL4218 led - isolated DIAC - output Gate-kathode thyristor 2(negative cycle



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    FvM
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    scr rectifier

    The IL4218 should be suitable for thyristor control. I would use a snubber anyway, as suggested in the datasheet. Also, the optotriac output should have a series diode to prevent from triggering with negative thyristor input voltage, otherwise the circuit could be destroyed. umery2k75 recently demonstrated how to with a moc3020 and a thyristor.



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    half controlled SCR rectifier

    I have used application control circuit for TCA785.
    the symitrical type schema used in our application.
    can you plaese give the half controlled rectifier schematic for tca785?


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    Re: half controlled SCR rectifier

    in which condition that we choose pulse transformer or opto-triacs for triggering?



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